Selenium-enriched yeast enhances dihydrochalcone biosynthesis, leaf growth, and heavy metal antagonism in Lithocarpus litseifolius by physiological, hormonal, and transcriptional analyses

Selenium (Se) element predominantly modulates plant biological functions through its diverse chemical forms. Se-enriched yeast (SeY) exhibits a novel organic Se form that attracts attention worldwide owing to its high bioavailability, with potential agricultural applications of animal feed industries or health products. However, the elicitation impacts of SeY on medicinal plants remain largely unknown. Herein, the regulatory effects of SeY were investigated using Lithocarpus litseifolius , a valuable medicinal and tea plant known for its sweet flavor and hypoglycemic properties, through physiological, hormonal and transcriptional analyses. The foliar application of SeY simultaneously promotes leaf dihydrochalcone (DHC) biosynthesis (particulally trilobatin, with a 4.07-fold increase within 15 days), photosynthetic and antioxidant systems, raises the total and organic Se levels, while reducing heavy metal (HM) accumulation in L. litseifolius seedling leaves. Moreover, diverse hormone profiles linked to physiological changes, including abscisic acid, indoleacetic acid conjugates, ethylene, gibberellins and strigolactone, have been triggered by SeY. An RNA-seq analysis reveals that differentially-expressed genes in the DHC metabolism ( 4-Coumarate-CoA ligase , and cinnamate 4-hydroxylase ), photosynthesis ( PsbX ), HM metabolism ( ATP-binding cassette C ), Se metabolism, antioxidant systems and transcription factor regulation (ethylene responsive factors and MYBs) are critical in SeY-induced molecular pathways. These findings demonstrate that SeY may function as a novel elicitor for enhancing leaf yield and bioactive quality, promoting Se biofortification, and ensuring medicine safety in L. litseifolius , primarily through a variety of physiological, hormonal and transcriptional pathways. Our study suggests the potential applications of SeY in the cultivation of medicinal crops. • SeY enhanced dihydrochalcone biosynthesis and leaf growth in L. litseifolius. • Organic Se and antioxidant system was boosted while Pb and As were reduced by SeY. • SeY triggered hormone crosstalks, such as increased ABA, IAA conjugate and ACC levels. • Transcriptional profilings in SeY-elicited pathways were revealed by RNA-seq. • SeY up-expressed 4CL, UGTs, PsbX, TCX, ABCC, METE, LHT, SULTR, PER, MYBs and ERFs .